I want to know if it's moderately easy to create an avatar system that works in 3D instead of 3D images, for example we currently use a 2D avatar system with a catalog where you can purchase items, but before exiting beta we would like to have 3D render characters. As a 3D artist I have no problem in creating these but putting them into the browser as a character is a different story.

If anyone knows some keywords I can search into for this or any help at all no matter how vague such as the programming language or methods of doing this, please share and I'll be very grateful!

Sounds like x3dom (http://www.x3dom.org) could be the right thing for you. It is basically an xml-encoded scene graph embedded in html. It relies only on WebGL+JS, i.e. no plugins at all, the customers only need a reasonably up-to-date browser. It is also declarative, i.e. you don't have to 'code' the graphics part, you just specify what should appear where.

I work in the same department as the people developing it, so I might be biased, but you should definately check it out.